This invention relates to an adjustable pin guide for use in screen printing, and more particularly to structure incorporated in a screen frame for adjusting the frame relative to an upright pin of a conventional pin bar.
In multi-color screen printing, it is necessary that each of the color screens be properly aligned with respect to one another, and also the screens in a particular sequence be aligned with respect to a printing platen so as to print a clear, high quality image.
For screen printing of garments, frames are often used to hold the screens, each frame holding a particular screen associated with one printing color. The frames thus aid an operator in handling the screens during the printing process. However, adjusting the frames relative to one another if the frames become warped, or the screens shift in the frames in some manner during their useful life remains a problem.
Several prior art patents describe mechanisms for registering a series of screens at the time they are made, but these patents do not recognize the problem of being able to later adjust a screen with respect to either upright pins, a worktable, or with other screens in a sequence. For instance, U.S. Pat. No. 2,444,860 to Summer, and U.S. Pat. No. 3,513,775 to Guthrie, illustrate mechanisms for aligning screens in original registration, but these devices provide no means for later adjusting the screens if they become warped or shifted in some manner. Presently, if one of the frames holding a screen is not aligned with the rest of the frames in a sequence, the associated screen is usually destroyed and a new screen is fixed on a frame and prepared in proper registration with the series. This is a time consuming and expensive process.
There are alignment mechanisms known which permit frames to be adjusted along one axis. For instance, U.S. Pat. No. 4,738,909 to Jennings illustrates a device for registering a screen with a plurality of upright registration pins mounted on a registration plate also known as a pin bar. With this device, which clamps to the edge of a frame, realignment movement is restricted to movement in a direction parallel with an edge of the frame. Rotating the frame, or moving the frame in direction perpendicular to the clamped edge, are adjustment movements that cannot be accommodated with the structure described in this patent.
There remains a clear need to be able to move a screen frame in any planar direction in order to adjust the single frame relative to a sequence of frames in a particular series, or to adjust a frame relative to the upright pins on a pin bar, layout board, or screen printing machine.